I often link a job to a separate workspace purely as a way of transferring parameters. I then clone the job, and unlink, leaving a copy in the new workspace with the same parameters.
I just did this with a job that had been queued but not run, and it was possible to link it to the new workspace, but not to unlink it (the option is grayed out). This seems like a (fairly minor) bug?
You’re correct, you can’t unlink a job that’s in “queued”, “waiting”, or “running” status. You will have to kill it, wait for it to complete, or clear it first. Based on your intentions, I think a better option would be for you to first clone the job, then use the “Move” action to move the cloned job into the new workspace. This saves you a step of having to unlink the original job.